Treatment of cardiogenic shock with the Hemopump left ventricular assist device

Temporary mechanical circulatory support & enhancing recovery after cardiac surgery

PURPOSE OF REVIEW

This review highlights the integration of enhanced recovery principles with temporary mechanical circulatory support associated with adult cardiac surgery.

RECENT FINDINGS

Enhanced recovery elements and efforts have been associated with improvements in quality and value. Temporary mechanical circulatory support technologies have been successfully employed, improved, and the value of their proactive use to maintain hemodynamic goals and preserve long-term myocardial function is accruing.

SUMMARY

Temporary mechanical circulatory support devices promise to enhance recovery by mitigating the risk of complications, such as postcardiotomy cardiogenic shock, organ dysfunction, and death, associated with adult cardiac surgery.

The Evolution of Durable, Implantable Axial-Flow Rotary Blood Pumps

Left ventricular assist devices (LVADs) are increasingly used to treat patients with end-stage heart failure. Implantable LVADs were initially developed in the 1960s and 1970s. Because of technological constraints, early LVADs had limited durability (eg, membrane or valve failure) and poor biocompatibility (eg, driveline infections and high rates of hemolysis caused by high shear rates). As the technology has improved over the past 50 years, contemporary rotary LVADs have become smaller, more durable, and less likely to result in infection. A better understanding of hemodynamics and end-organ perfusion also has driven research into the enhanced functionality of rotary LVADs. This paper reviews from a historical perspective some of the most influential axial-flow rotary blood pumps to date, from benchtop conception to clinical implementation. The history of mechanical circulatory support devices includes improvements related to the mechanical, anatomical, and physiologic aspects of these devices. In addition, areas for further improvement are discussed, as are important future directions-such as the development of miniature and partial-support LVADs, which are less invasive because of their compact size. The ongoing development and optimization of these pumps may increase long-term LVAD use and promote early intervention in the treatment of patients with heart failure.

The Hemopump™, The First Intravascular Ventricular Assist Device

Development of durable left ventricular assist devices (LVADs), based on rotary flow blood pumps, began in earnest after the successful implantation of a catheter-mounted axial flow blood pump via intravascular access in 1988. This device, the Hemopump, successfully supported the circulation of a patient in cardiogenic shock secondary to acute rejection of a transplanted heart. Duration of support was 46 hours, resulting in complete recovery of cardiac function and hospital discharge. In effect, this sentinel event demonstrated that continuous-flow blood pumps could be used to support patients in cardiogenic shock. This held true in spite of many widely held paradigms against rotary blood pumps regarding blood damage, diminished pulsatility, and thrombosis. At this writing, 50,000 patients have been implanted with durable LVADs based on rotary blood pumps as a bridge to cardiac transplantation or destination support as long as 10 years.

The Enabler Cannula Pump: A Novel Circulatory Support System

Background

The enabler circulatory support system is a catheter pump which expels blood from the left or right ventricular cavity and provides pulsatile flow in the ascending aorta or pulmonary artery. It is driven by a bedside installed pulsatile driving console. The device can easily be implanted by a minimal invasive approach, similar to the Hemopump.

Purpose

To demonstrate the hemodynamic performance of this new intracardiac support system.

Methods

In a series of 9 sheep, hemodynamic evolutions were recorded in various conditions of myocardial contractility (the non-failing, the moderately failing and the severely failing heart). Heart failure was induced by injection of microspheres in the coronary arteries.

Results

Introduction of the cannula through the aortic valve was feasible in all cases. Pump flow by the enabler was gradually increased to a maximum of 3.5 L/min. Diastolic (and mean) aortic blood pressure is significantly increased in the non-failing and moderately failing condition (counterpulsation mode). In heart failure, cardiac output is significantly increased by the pump (p<0.0001). A drop in left atrial pressure (indicating unloading) is achieved in all conditions but reaches significant levels only during heart failure (p=0.0068).

Conclusions

This new circulatory support system contributes to stabilization of the circulation in the presence of cardiac unloading. In heart failure it actually supports the circulation by increasing cardiac output and perfusion pressure.

Hydraulic Refinement of An Intraarterial Microaxial Blood Pump

Intravascularly operating microaxial pumps have been introduced clinically proving to be useful tools for cardiac assist (1–4). However, a number of complications have been reported in literature associated with the extra-corporeal motor and the flexible drive shaft cable (5,6). In this paper, a new pump concept is presented which has been mechanically and hydraulically refined during the developing process. The drive shaft cable has been replaced by a proximally integrated micro electric motor and an extra-corporeal power supply (7). The conduit between pump and power supply consists of only an electrical power cable within the catheter resulting in a device which is indifferent to kinking and small curvature radii. Anticipated insertion difficulties, as a result of a large outer pump diameter, led to a two-step approach with an initial 6,4mm pump version and a secondary 5,4mm version. Both pumps meet the hydraulic requirement of at least 2.5I/min at a differential pressure of 80–100mmHg. The hydraulic refinements necessary to achieve the anticipated goal are based on ongoing hydrodynamic studies of the flow inside the pumps. Flow visualization on a 10:1 scale model as well as on 1:1 scale pumps have yielded significant improvements in the overall hydraulic performance of the pumps. One example of this iterative developing process by means of geometrical changes on the basis of flow visualization is illustrated for the 6.4mm pump.

Preoperative Invasive Hemodynamic Determinants of Survival Among Patients Undergoing Aortic or Mitral Valve Surgery

OBJECTIVES

To evaluate the association of preoperative invasive hemodynamic parameters with mortality in valvular heart surgery.

DESIGN

Retrospective cohort study.

SETTING

Single tertiary academic medical center.

PARTICIPANTS

A total of 382 patients who underwent preoperative right and/or left heart catheterization before open aortic valve replacement (AVR), open mitral valve repair/replacement (MVR), or combined AVR and MVR, from July 2009 to December 2014.

INTERVENTIONS

Retrospective chart review.

MEASUREMENTS AND MAIN RESULTS

Common hemodynamic indices derived from direct catheterization measurements were assessed, including pulmonary artery systolic pressure (PASP), pulmonary artery pulse pressure (PPP), mean pulmonary capillary wedge pressure (mPCWP), pulmonary artery pulsatility index, diastolic pressure gradient, left ventricular work index, and right ventricular work index. Bivariable and multivariable associations of these measures with survival were determined using Cox proportional hazards regression. Kaplan-Meier survival curves were generated using the log-rank test. The median age of the cohort was 69 years (interquartile range 60-79 years), and 162 (42.4%) of the patients were female. Elevated PASP (hazard ratio [HR] 1.32 per 10 mmHg, p < 0.0001), elevated PPP (HR 1.48 per 10 mmHg, p < 0.0001), and elevated mPCWP (HR 1.95 per 10 mmHg, p < 0.0001) were all associated with decreased survival, as was decreased diastolic blood pressure (DBP) (p = 0.005). The combination of elevated PPP and decreased DBP was associated with the worst outcomes.

CONCLUSIONS

PASP, PPP, mPCWP, and DBP were significantly associated with mortality in valvular heart surgery patients. These hemodynamic parameters may be useful in risk stratification of this population subset.

A review of the fundamental principles and evidence base in the use of extracorporeal membrane oxygenation (ECMO) in critically ill adult patients

Extracorporeal membrane oxygenation (ECMO) comprises a commonly used method of extracorporeal life support. It has proven efficacy and is an accepted modality of care for isolated respiratory or cardiopulmonary failure in neonatal and pediatric populations. In adults, there are conflicting studies regarding its benefit, but it is possible that ECMO may be beneficial in certain adult populations beyond postcardiotomy heart failure. As such, all intensivists should be familiar with the evidence-base and principles of ECMO in adult population. The purpose of this article is to review the evidence and to describe the fundamental steps in initiating, adjusting, troubleshooting, and terminating ECMO so as to familiarize the intensivist with this modality.

Better outcome after cardiopulmonary resuscitation using percutaneous emergency circulatory support in non-coronary patients compared to those with myocardial infarction

BACKGROUND & OBJECTIVES

Mobile heart-lung-machines applied by percutaneous cannulation are mostly used in patients suffering from acute myocardial infarction (AMI). Whether patients with non-coronary reasons for circulatory arrest benefit of percutaneous emergency circulatory support (PECS) in the same way is still unclear.

METHODS

We included 22 consecutive patients who were treated by PECS during a registry period of two years. Primary study endpoint was 30-day mortality rate.

RESULTS

Circulatory arrest was caused by AMI in 14 patients (64%). The remaining 8 patients suffered from cardiomyopathy/myocarditis, 4; pulmonary embolism, 2; acute pulmonary failure, 1; and tumor lysis syndrome, 1. Revascularization rate was 93% in the AMI group under PECS support. Overall survival rate was 36.4% at one month: it reached 62.5% among non-coronary patients, but only 21.4% in the AMI group (P = 0.02). Weaning was possible by direct heart transplantation in two patients. Additional two patients required implantation of a left ventricular assist device. Pumpless extracorporeal lung assist was used in one case.

CONCLUSION

In this small retrospective study percutaneous emergency circulatory support provided sufficient hemodynamic stabilization in emergency situations. One fifth of AMI patients were saved by immediate restoration of circulation and causal treatment when other means of resuscitation failed. Higher survival rates were noted in non-coronary patients.

Development of "plug and play" TransApical to aorta VAD

Our TransApical to Aorta pump, a simple and minimally invasive left ventricular (LV) assist device, has a flexible, thin-wall conduit connected by six struts to a motor with ball bearings and a turbine extending into the blood path. Pulsatile flow is inherent in the design as the native heart contraction preloads the turbine. In six healthy sheep, the LV apex was exposed by a fifth intercostal left thoracotomy. The pump was inserted from the cardiac apex through the LV cavity into the ascending aorta. Aortic and LV pressure waveforms, pump flow, motor current, and pressure were directly measured. All six cannula pumps were smoothly advanced on the first attempt. Pump implantation was <15 minutes (13.6 +/- 1.8 minutes). Blood flow was 2.8 l/min to 4.4 l/min against 86 +/- 8.9 mm Hg mean arterial blood pressure at maximum flow. LV systemic pressure decreased significantly from 102.5 +/- 5.55 mm Hg to 58.8 +/- 15.5 mm Hg at the fourth hour of pumping (p = 0.042), and diastolic LV pressure decreased from 8.4 +/- 3.7 to 6.1 +/- 2.3 mm Hg (p > 0.05). The pump operated with a current of 0.4 to 0.7 amps and rotation speed of 28,000 to 33,000 rpm. Plasma free hemoglobin was 4 +/- 1.41 mg/dl (range, 2 to 5 mg/dl) at termination. No thrombosis was observed at necropsy.A left ventricular assist device using the transapical to aorta approach is quick, reliable, minimally invasive, and achieves significant LV unloading with minimal blood trauma.

Mechanical Circulatory Support for Cardiogenic Shock Complicating Acute Myocardial Infarction: An Experimental and Clinical Review

Cardiogenic shock (CS) occurs in 7% to 10% of cases after acute myocardial infarction and remains the most common cause of death in these patients. Despite aggressive treatment regimens such as fibrinolysis and percutaneous transluminal coronary angioplasty, mortality rates from CS remain extremely high. It has been shown that intra-aortic balloon pumping can result in initial hemodynamic stabilization. However, in the majority of studies, death was merely delayed. In recent years, efforts have been made to develop ventricular devices (LVAD) capable of providing complete short-term hemodynamic support. Seventeen major studies of LVAD support for CS complicating acute myocardial infarction are reported in the literature, with a mean weaning and survival rate of 58.5% and 40%, respectively. Patients considered in these studies are difficult to compare in terms of demographic and anatomic data, but taking these considerations into account, LVAD support seems to give no survival improvement in these patients compared with early reperfusion alone or associated with intra-aortic balloon pumping. Data emerging from experimental studies of acute myocardial infarction supported with LVAD are intriguing. In this review, we report the LVAD experience in the CS setting, starting from percutaneous extracorporeal support up to bridge therapy with implantable devices.

Systematic review of percutaneous cardiopulmonary bypass for cardiac arrest or cardiogenic shock states

BACKGROUND

Cardiogenic shock and cardiac arrest are common, lethal, debilitating and costly. Percutaneous cardiopulmonary bypass is an innovative strategy for treating these disorders that consists of rapid initiation of cardiopulmonary bypass and extracorporeal maintenance of circulation until restoration of an effective cardiac output. Multiple case reports suggest that percutaneous bypass is efficacious in patients with these disorders but these experiences have not been collated. Therefore, we have reviewed systematically the published experience with percutaneous bypass in patients with cardiogenic shock or cardiac arrest.

OBJECTIVES

The objectives were to describe the proportion of patients with cardiogenic shock or cardiac arrest who achieved restoration of spontaneous circulation or survival to discharge with percutaneous bypass. A secondary objective was to describe adverse effects associated with percutaneous bypass, if feasible.

DESIGN

Articles were identified by using a comprehensive search of English-language MEDLINE from 1966 to September 2005.

PATIENTS

Individuals in cardiogenic shock or cardiac arrest.

INTERVENTIONS

Percutaneous cardiopulmonary bypass.

ANALYSIS

Effects were summarized as inverse-variance weighted means, standard errors, median and interquartile range.

RESULTS

Included were 85 studies of 1494 patients with cardiogenic shock, cardiac arrest or both. Studies were case reports, case-series or case-control studies of heterogeneous interventions in heterogeneous patients. The proportion of patients weaned was mean, 76.8+/-4.2%, and median, 66.0% (IQR 50%, 100%). The proportion of patients who survived to discharge was mean, 47.4+/-4.5%, and median 40.0% (IQR 20%, 75%). Fifty-two studies included 533 patients in cardiogenic shock. The proportion of patients who survived to discharge was mean, 51.6+/-6.5%, and median 38.5% (IQR 23.4%, 76.3%). Fifty-four studies included 675 patients in cardiac arrest. The proportion of patients who survived to discharge was mean, 44.9+/-6.7%, and median, 42.3% (IQR 15.4%, 75%). Five studies with 286 subjects had both patients with cardiogenic shock or cardiac arrest.

CONCLUSIONS

Percutaneous bypass is an efficacious intervention in patients with cardiac arrest or cardiogenic shock. Adequately-powered experimental studies of current percutaneous bypass technologies are required to demonstrate whether it is safe, effective and cost-effective.

Hemodynamic Effects of a New Percutaneous Circulatory Support Device in a Left Ventricular Failure Model

We have tested a new percutaneous circulatory support device in seven anesthetized calves with induced left ventricular failure. The device is based on a flexible catheter with a foldable propeller and cage at the distal end. The rotation of the propeller (1,000-15,000 rpm) is transmitted from a drive unit at the proximal end to the propeller by way of a rotating wire inside the catheter. This also contains an umbrella-like mechanism to open the pump head from the folded (diameter 4.6 mm) to the active position. The rotation of the propeller creates a pressure drop in front of the propeller and a pressure rise behind. Heart failure was induced with metoprolol and verapamil in combination with a VVI pacemaker to create a left atrial pressure greater than 20 mm Hg. A centrifugal pump was used to bypass the right ventricle and to ensure a sufficient filling of the left ventricle. After baseline recordings, the pump was run at 14,000 rpm, and the hemodynamic response was compared with the baseline. A 24 +/- 10 mm Hg pressure gradient was generated across the pump, resulting in a drop in the right carotid artery mean pressure from 80 +/- 11 to 71 +/- 13 mm Hg (p = 0.008) and a drop in the left ventricular systolic pressure from 109 +/- 17 to 100 +/- 19 mm Hg (p = 0.004). The pressure in the left atrium decreased from 25 +/- 3 to 20 +/- 5 mm Hg (p = 0.008). The mean femoral pressure increased from 78 +/- 10 to 95 +/- 20 mm Hg (p = 0.005). A moderate reduction in the right carotid flow was observed (15%, p = 0.029), whereas no significant changes were found in the coronary flow, the flow in the right femoral artery, or in the left kidney. The device showed a significant unloading of the left ventricle and an increased perfusion pressure for the lower part of the body. The moderate changes in flow were probably caused by still active autoregulation, and this needs to be tested with more pronounced circulatory failure.

From a lab type to a product: a retrospective view on Impella's assist technology

A lab type is best described by its value as a result of its handcrafted uniqueness in small numbers. Logically, there is not one lab type like another, and the fact that it has been realized does not mean that this special effort can be easily reproduced. Furthermore, most lab types have undergone stand alone test runs revealing fingerprints rather than universal results at a 20% effort to 80% effect ratio. A product development, on the other hand, is best described by an 80% effort to 20% effect ratio in terms of measurable results. Products are producible and cost effective goods which are well documented and have undergone numerous test runs and test procedures assuring safety and quality, a basic requirement for market approval and cost effective marking. Based on the intravascular pump technology, comprising a sensorized axial flow pump with an integrated micromotor, the iterative dependence of the product development on lab types is demonstrated showing in particular the importance of having highly developed lab types before initiating the product development. By example, we demonstrated that high product quality has a greater impact on the reduction of blood damage than numerous redesigns. Reengineering issues are addressed, which are part of the product development process. Furthermore, the previously mentioned technology serves as a platform leading directly from the perioperative biventricular system to a 7 day pump as well as a miniaturized 12 Fr version.

Research and development of an implantable, axial-flow left ventricular assist device: the Jarvik 2000 Heart

Advances in technology and increased clinical need have led to the development of a new type of blood pump. The Jarvik 2000 Heart is an electrically powered, axial-flow left ventricular assist device that has been developed during the past 13 years. Unlike first-generation left ventricular assist devices, which were developed in the 1970s and were designed to totally capture the cardiac output, the Jarvik 2000 is designed to normalize the cardiac output by augmenting the function of the chronically failed heart for extended periods. Design iterations have been tested in 67 animals, and clinical trials have recently begun. Three patients have received the Jarvik 2000 as a bridge to transplantation, and 1 patient is being supported permanently outside the hospital. All 4 patients have improved from New York Heart Association functional class IV to class I, and 2 of them have been discharged from the hospital after heart transplantation. The experimental and clinical results indicate that the Jarvik 2000 can provide physiologic support with minimal complications and is reliable, biocompatible, and easy to implant.

Bridge to recovery for postcardiotomy failure: is there still a role for centrifugal pumps?

BACKGROUND

Early implantation of centrifugal devices in patients with postcardiotomy cardiogenic shock may provide a bridge to recovery and allow subsequent long-term survival.

METHODS

Since January 1989, 62 patients were supported with centrifugal pumps because of failure to wean from cardiopulmonary bypass. Indications were postcardiotomy cardiogenic shock (PCCS) (n = 60), bridge to cardiac retransplantation (n = 1), and right ventricular failure (n = 1). Patients' ages ranged from 23 to 78 years; 40 were men (65%), and 22 were women (35%). Twenty-two patients (35%) had a left ventricular assist device; 9 patients (15%) had a right ventricular assist device; and 31 patients (50%) had a biventricular assist device. Length of support ranged from 1 day to 19 days.

RESULTS

Forty-two patients (68%) were weaned successfully; 27 patients survived to discharge (44%). Complications included bleeding (n = 41, 66%), renal failure (n = 28, 45%), and respiratory failure (n = 26, 42%). Currently, 23 patients survived 10 or more years (n = 1), 6 to 10 years (n = 7), 1 to 5 years (n = 10), and less than 1 year (n = 5).

CONCLUSIONS

Centrifugal pumps are available, easy to use, and relatively inexpensive. Our experience justifies their continued use as a bridge to recovery for patients with postcardiotomy cardiogenic shock, despite the availability and increasing use of more expensive devices.

Mechanical support for postcardiotomy cardiogenic shock

Postcardiotomy cardiogenic shock (PCCS) results in substantial morbidity and mortality. Despite intraaortic balloon pump and inotropic support, some patients with PCCS continue to have a refractory low cardiac output. For these patients, more effective ventricular assistance is imperative to prevent death. Multiple systems are available for the short-term support of patients with PCCS. Regardless of the device employed, only 25% of these patients survive and are discharged home. Two strategies, however, may improve the outcome of PCCS. One is long-term support by an implantable assist device, which can allow optimal ventricular unloading. Unfortunately, not all cardiac surgery centers offer this type of support. Therefore, the other strategy is the creation of postcardiotomy referral centers that offer long-term support or heart transplantation. Such centers would conserve scarce donor organs, maximize the chance of myocardial recovery, and yield expertise applicable not only to device recipients but also to critically ill heart-failure patients who do not need an implantable pump.

The intra-aortic cannula pump: A novel assist device for the acutely failing heart

OBJECTIVE

The intra-aortic cannula pump is a catheter pump designed to support the acutely failing heart. It expels blood from the left ventricle into the ascending aorta in a pulsatile flow pattern. The aim of the study was to analyze the hemodynamic performance of this new intracardiac support system in acute heart failure.

METHODS

A 24F cannula was studied in a series of 16 sheep. Hemodynamic changes were assessed in the nonfailing, the moderately failing, and the severely failing heart. Heart failure was induced by an injection of microspheres into the left anterior descending coronary artery. The cannula was inserted through the aortic arch and introduced through the aortic valve into the left ventricle.

RESULTS

Cannula insertion was feasible in all animals. Flow through the intra-aortic cannula flow was increased to a maximum of 3 L/min. No hemodynamic changes were observed in the nonfailing heart. A significant increase in cardiac output was observed in the moderately and severely reduced left ventricle (2.67 +/- 0.7 L to 3.51 +/- 0.83 L; P =.001; and 1.18 +/- 0.77 L to 2.43 +/- 0.44 L; P =.001, respectively). A drop in left atrial pressure was achieved in moderate and severe heart failure (14.1 +/- 5.93 mm Hg to 9.71 +/- 2.63 mm Hg; P =.0001; and 23 +/- 7.16 mm Hg to 11.2 +/- 2.55 mm Hg; P = 0.0001, respectively). Systolic and diastolic systemic blood pressures increased in the severely failing heart (57.3 +/- 12.8 mm Hg to 75.4 +/- 11.2 mm Hg; P =.0001; and 35.6 +/- 8.2 mm Hg to 60 +/- 14.3 mm Hg; P =.0006, respectively).

CONCLUSIONS

Hemodynamic data demonstrate the beneficial effects of the intra-aortic cannula pump in moderate and severe heart failure. The intra-aortic cannula pump represents a new modality for the treatment of acute heart failure.

[Reperfusion therapy and mechanical circulatory support in patients in cardiogenic shock]

Cardiogenic shock is a state of inadequate tissue perfusion due to cardiac dysfunction, which is most commonly caused by acute myocardial infarction. The pathophysiology of cardiogenic shock is characterized by a downward spiral: ischemia causes myocardial dysfunction, which, in turn, augments the ischemic damage and the energetical imbalance. With conservative therapy, mortality rates for patients with cardiogenic shock are frustratingly high reaching more than 80%. Additional thrombolytic therapy has not been shown to significantly improve survival in such patients. Emergency cardiac catheterization and coronary angioplasty, however, seem to improve the outcome in shock-patients, which most probably is due to rapid and complete revascularization generally reached by angioplasty. In addition to interventional therapy with rapid coronary revascularization, the use of mechanical circulatory support may interrupt the vicious cycle in cardiogenic shock by stabilizing hemodynamics and the metabolic situation. Different cardiac assist devices are available for cardiologists and cardiac surgeons: 1. intraaortic balloon counterpulsation (IABP), 2. implantable turbine-pump (Hemopump), 3. percutaneous cardiopulmonary bypass support (CPS), 4. right heart, left heart, or biventricular assist devices placed by thoracotomy, and 5. intra- and extrathoracic total artificial hearts. Since percutaneous application is possible with IABP, Hemopump and CPS, these devices are currently used in interventional cardiology. The basic goals of the less invasive intraaortic balloon counterpulsation (IABP; Figure 1) are to stabilize circulatory collapse, to increase coronary perfusion and myocardial oxygen supply, and to decrease left ventricular workload and myocardial oxygen demand (Figure 2). Since the advent of percutaneous placement, IABP has been used by an increasing number of institutions (Figure 3). In addition to cardiogenic shock, the system may be of use in a variety of other indications in the catheterization laboratory and intensive care unit, including weaning from percutaneous cardiopulmonary bypass, in ischaemic left ventricular failure, in unstable angina, in high risk PTCA, and in prophylactic support in patients with myocardial infarction and successful revascularization. Animal experimental data showed that IABP may improve success of thrombolysis and recent clinical data suggest that survival is enhanced and transfer for revascularization is facilitated when patients with myocardial infarction and cardiogenic shock undergo thrombolysis and IABP rather than thrombolysis alone. A lot of studies had demonstrated before, that combined use of counterpulsation and revascularization therapy (i.e. coronary bypass surgery or angioplasty) may improve prognosis in patients with myocardial infarction complicated by cardiogenic shock (Table 1). In such patients, early treatment with IABP is most important: Multivariate analysis identified early IABP-support with a duration of shock to IABP-treatment of > or = 4 hours as an independent predictor of a positive short-term outcome. In shock-patients with postinfarction ventricular septal defect, IABP provides a marked hemodynamic improvement, and a significant decrease in shunt-flow (Figure 5). However, despite initial stabilization with IABP, such patients need immediate surgical repair of the septal defect to avoid hemodynamic deterioration. The rate of complications related to percutaneous IABP was significantly attenuated by employing catheters of reduced size. Using 9.5-F catheters, a long duration of counterpulsation emerged as the most significant factor associated with complications. In our hospital, those patients with 9.5-F catheters in whom counterpulsation did not exceed 48 hours had a low complication rate of 3.9%. The Hemopump is a catheter-mounted transvalvular left ventricular assist device intended for surgical placement via the femoral artery (Figures 6 and 7). (ABSTRACT TRUNCATED)

A sealless centrifugal blood pump with passive magnetic and hydrodynamic bearings

We are developing a permanently implantable ventricular assist system based on a sealless centrifugal blood pump. The impeller of the pump is supported by a passive radial magnetic bearing acting in synergy with hydrodynamic bearings. Torque is transmitted to the impeller by electromagnetic coupling via an integrated axial flux gap motor. Computer modeling has been used extensively to guide the hydraulic and electromagnetic design of the pump. As part of the development effort, a prototype system was built, which consisted of a radial magnetic bearing, an axial air gap motor, and a pivot bearing to constrain the axial motion. The following testing has been completed to validate the design. First, hydraulic tests have demonstrated sufficient hydraulic performance. Second, preliminary in vitro evaluation of hemolysis was low compared to that of a BioPump control. Third, a 6 h in vivo experiment was successfully completed.

The Hemopump in 1997: a clinical, political, and marketing evolution

BACKGROUND

The Hemopump (Medtronic, Inc, Minneapolis, MN) was conceived in 1975 and designed in 1982 as a temporary, extracorporeal cardiac assist system. Although it has been used clinically in Europe, it is not currently available in the United States.

METHODS

In vitro and in vivo testing of the Hemopump began in 1983. Clinical investigations have included studies of patients in cardiogenic shock, Hemopump-supported coronary artery bypass operations in Sweden, and European studies of percutaneous transluminal coronary angioplasty (PTCA) with Hemopump support.

RESULTS

The Hemopump has demonstrated positive hemodynamic effects in patients. Laboratory and clinical studies have shown that the nonpulsatile axial flow generates flows of up to 4.5 L/min while maintaining adequate perfusion of other organs. In Europe, hemopumps have been used successfully to support coronary bypass and PTCA.

CONCLUSIONS

The Hemopump system is simple, inexpensive, and well tolerated by the blood elements. Moreover, its design allows flexibility in supporting patients during cardiopulmonary bypass (in lieu of conventional techniques) and high risk angioplasty, as well as in rescuing patients with low cardiac output.

Mechanical circulatory support devices in the treatment of heart failure

With an increasingly aging population, heart failure is a major health issue, affecting more than 10% of the population over 65 years of age, and costing hundreds of millions of dollars per year for ongoing care. Even with maximal medical therapy, annual mortality rates of in excess of 25% are commonly reported. Over the last three decades, various surgical approaches have been examined in the hope of improving the outcome of congestive cardiac failure. These procedures range from simple coronary revascularisation to left ventricular reduction surgery and cardiac transplantation. Although of value in selected situations, no surgical approach, beyond transplantation, has had significant impact on the outcome of heart failure. In the last decade, development in the area of mechanical support for the failing heart has continued to expand at a rapid rate. Strong evidence now exists to show that in many patients with advanced heart failure, prolonged mechanical support results in significant myocardial recovery. There are currently several mechanical support devices available for clinical use, although most are considered experimental in this country. These devices are expensive and are not without significant complications, but early results of their use as either a bridge to transplantation or as a stand alone treatment, have been very encouraging. Currently available mechanical assist devices are described, with discussion of indications for implantation, complications and results of their use.

Clinical experience with the percutaneous hemopump during high-risk coronary angioplasty

The percutaneous Hemopump showed beneficial effects during coronary angioplasty in 32 high-risk patients with unloading of the left ventricle during ischemia and maintaining cardiac output with mean aortic pressures of 50 mm Hg in case of cardiac arrest (3 patients). High procedure-related morbidity (occlusion of femoral artery in 2 patients; bleeding with need of transfusion in 4 patients) and mortality (4 of 32 patients) rates demonstrate the need for a very careful selection of patients.

Mechanical Support After Cardiac Surgery

The need for mechanical circulatory support after car diac surgery is uncommon despite an older and increas ingly sicker patient population. From September 1992 through January 1997, surgeons performed 21,000 car diac operations at the Cleveland Clinic Foundation, and mechanical support postcardiotomy was required in only 75 patients (0.3%). Aggressive management of cardiac and pulmonary dysfunction usually results in successful weaning from cardiopulmonary bypass. How ever, when mechanical support is needed, it can tax the resources of the institution and requires integrated patient management from the entire health care team. Management of postcardiotomy circulatory failure will be discussed in detail, along with the devices commer cially available for both short- and long-term support. Copyrighr© 1998 by W. B. Saunders Company.

The continuing evolution of mechanical ventricular assistance

A great number of patients suffer and die of the sequelae of acute and chronic heart failure each year. Although advances in medical and surgical therapy have benefited many of these patients, most have disease that is refractory to any definitive therapy. For these patients cardiac transplantation is the only remaining hope. Unfortunately, because of the increasing demand for donor organs in the face of a fixed and limited supply, this option is available to only a small percentage of these patients. Even in patients accepted for transplantation, a significant waiting list mortality has been observed. A variety of VADs have been developed since the first successful case of mechanical cardiac assistance more than 30 years ago. These devices differ in basic mechanical function, method of insertion, and degree of implantability and thus have different indications and potential applications. Whereas the intraaortic balloon pump and centrifugal pumps are effective short-term support modalities, extracorporeal and implantable pulsatile devices have been used successfully for long-term support of patients with reversible and nonreversible cardiac failure. Although these pumps have most commonly been used as bridges to transplantation, increasing clinical experience has supported the notion of long-term mechanical assistance as a definitive therapy for patients with end-stage heart disease. Although complications, particularly infection and thromboembolism, pose significant challenges and long-term device reliability remains to be fully determined, available implantable devices appear to be capable of providing effective long-term support. As data are obtained from currently ongoing trials comparing VAD support with medical therapy for end-stage heart failure, ethical and economic issues will assume increasing importance.

Flow characteristics of the Hemopump: an experimental in vitro study

BACKGROUND

The Hemopump (DLP/Medtronic) has been in clinical use for about 7 years. There is still no adequate way of determining actual output from the three available pump systems in the clinical situation. If the pump is completely stopped during weaning from the device, there is a possibility of back-leakage through the pump, endangering the patient from regurgitation into the left ventricle. It can also make it more difficult to judge the recovery of heart function because of a volume load of the left ventricle. The aim of this study was to evaluate in a standardized, experimental in vitro model the output from three different-sized Hemopump catheters at various pressure levels and to quantify the back-flow through the pumps.

METHODS

The Hemopump models were tested in an in vitro study regarding total outflow at various speeds at three pressure levels. The back-flow through the pumps was also measured with the pumps at a complete stop.

RESULTS

The outflow from the Hemopumps ranged from 0.4 to 4.5 L/min, depending on which pump and speed were used. Variations in total output, depending on speed and various pressure settings, could be up to 0.4 L/min. Back-flow through the pump into the left ventricle may be as great as 1.6 L/min.

CONCLUSIONS

The flow outputs from the different Hemopump models were reproducible over time and were closely related to the resistance of the model. The Hemopump, if not running, can induce substantial regurgitation through the pump into the left ventricle.

Feasibility of an air motor-driven centrifugal blood-pumping system

The use of cardiopulmonary bypass (CPB) is extending out of the cardiac surgery operating room into new venues. The long-term goal of this project is the development of a completely disposable temporary-use CPB system that could be economically distributed to all of the units where it might be needed. Centrifugal blood pumps have demonstrated successful and widespread use. However, they are not as widely available as might be desired because they require a large and expensive console. An inexpensive, small, lightweight, disposable unit, in contrast, could be widely distributed for emergency care of patients and would be logistically practical for patient transportation between the presenting institution and a major cardiac care facility equipped for definitive treatment. An air motor might be an approach to such a device. The current research project underway at the University of Akron in conjunction with the Cleveland Clinic Foundation has focused on the following key feasibility issues: air consumption, air motor noise, and sealing the rotating shaft. Prototypes have been constructed from commercially available vane and turbine motors. Early studies have demonstrated favorable results with regard to air consumption and shaft sealing and directions for handling air motor noise.

Mechanical circulatory assist devices

A ventricular assist device (VAD) is a heterotopic mechanical pump that augments or replaces the output of a failing ventricle. In the past decade, investigation and use of these devices has greatly improved our understanding of their potential roles and limitations. Successful univentricular and biventricular support has allowed for myocardial recovery and survival in several settings of intractable cardiogenic shock. The development of long-term VADs has allowed for successful bridging of patients to heart transplantation, and it has laid the groundwork for a permanent implantable replacement ventricle. In this review, we address indications, complications, management, and results of mechanical support in postcardiotomy, bridge to recovery, and bridge to transplantation settings. The tools to achieve ventricular support in the United States, and the VADs themselves, are described, with emphasis on unique features, indications, and limitations.

Hemopump treatment in patients with postcardiotomy heart failure

BACKGROUND

This study examined the use of the Hemopump to treat low cardiac output syndrome after cardiopulmonary bypass.

METHODS

We used the Hemopump temporary cardiac assist system in 29 patients with severe left ventricular dysfunction after open heart operations from September 1991 to November 1994.

RESULTS

Five patients were excluded from the study due to initial patient/device-related problems. Ten patients died in the operating room or early during the stay in the intensive care unit due to progressive biventricular failure. Fourteen patients (58.3%) were weaned from the device, and all of them were later discharged. In a subgroup of patients (54%) in whom we had a more aggressive approach for early insertion of the pump, the survival rate was 85%. Preoperative Higging risk score was significantly related to survival.

CONCLUSIONS

The Hemopump can effectively unload a failing left ventricle with preservation of multiorgan perfusion. A minor decrease in kidney function was observed in most patients, but none of the surviving patients needed hemodialysis. One patient required a short period of peritoneal dialysis to get rid of fluid overload. Hemolysis or platelet dysfunction was not a clinical problem.

Left ventricular assistance with the transthoracic 24F Hemopump for recovery of the failing heart

BACKGROUND

The Hemopump was developed as a more powerful assist device for postcardiotomy support in patients in whom the intraaortic balloon pump is insufficient.

METHODS

Over a 2-year period 21 (0.8%) of 2,585 patients undergoing cardiac operations needed a ventricular assist device because of postcardiotomy heart failure unresponsive to pharmacologic and intraaortic balloon support. Sixteen of these patients were assisted with the 24F transthoracic Hemopump left ventricular assist device. The aim of the mechanical support was myocardial recovery as the underlying conditions (age, arterial hypertension, diabetes, vascular and pulmonary disease) excluded heart transplantation.

RESULTS

Hemodynamic improvement was apparent with a decrease in left atrial pressure (mean, 18.6 to 9.2 mm Hg), an increase in arterial blood pressure (mean, 54.1 to 70.1 mm Hg), and an increase in cardiac index. Five patients died within the first 24 hours because of low cardiac output. Although the heart was well unloaded (decrease in left atrial pressure of 8 +/- 4.69 mm Hg versus 9.3 +/- 5.51 mm Hg for the other patients), the increase in cardiac index was significantly lower (+0.516 versus +1.377 L.min-1.m-2; p = 0.027). Three of these 5 patients were known to have severe left ventricular hypertrophy. Of the remaining 11 patients, 2 were assisted for 1 week but failed to show recovery of the myocardium, 8 (50%) were weaned, and 4 (25%) were discharged. There were no device-related complications except the thrombosis of a cannula that was left for 10 days.

CONCLUSIONS

The transthoracic Hemopump is an easy-to-use and reliable assist device. Left ventricular hypertrophy is a relative contraindication for the use of the Hemopump.

Development of an axial flow ventricular assist device: in vitro and in vivo evaluation

A collaborative effort between Baylor College of Medicine and NASA/Johnson Space Center is underway to develop an axial flow ventricular assist device (VAD). We evaluated inducer/impeller component designs in a series of in vitro hemolysis tests. As a result of computational fluid dynamic analysis, a flow inducer was added to the front of the pump impeller. According to the surface pressure distribution, the flow inducer blades were connected to the impeller long blades. This modification eliminated high negative pressure areas at the leading edge of the impeller. Comparative studies were performed between inducer blade sections that flowed smoothly into the impeller blades (continuous blades) and those that formed discrete separate pumping sections (discontinuous blades). The inducer/impeller with continuous blades showed significantly (p < 0.003) lower hemolysis with a normalized index of hemolysis (NIH) of 0.018 +/- 0.007 g/100 L (n = 3), compared with the discontinuous model, which demonstrated an NIH of 0.050 +/- 0.007 g/100 L (n = 3). The continuous blade model was evaluated in vivo for 2 days with no problems. One of the pumps evaluated ran for 5 days in vivo although thrombus formation was recognized on the flow straightener and the inducer/impeller. As a result of this study, the pump material was changed from polyether polyurethane to polycarbonate. The fabrication method was also changed to a computer numerically controlled (CNC) milling process with a final vapor polish. These changes resulted in an NIH of 0.0029 +/- 0.0009 g/100 L (n = 4), which is a significant (p < .0001) value 6 times less than that of the previous model.(ABSTRACT TRUNCATED AT 250 WORDS)

Concept, realization, and first in vitro testing of an intraarterial microaxial blood pump

Intravascular operating microaxial pumps have been clinically introduced (Hemopump 21; Hemopump 14) and have proven to be useful tools for cardiac assist. Due to device-related complications that are associated with the drive concept of an extracorporeal motor and a flexible drive shaft cable, a new pump concept is presented and has been refined in the development process. The cable is replace by a proximally attached drive unit and an extracorporeal power supply. In addition to ongoing hydrodynamic studies of the flow inside the pump and improvements of the overall hydraulic performance, a microelectric motor was realized and integrated. In vitro tests revealed the feasibility of such a concept.

Transvalvular left ventricular assistance in acute myocardial infarction with cardiogenic shock and high risk angioplasty: experimental and clinical results with the Hemopump

The Hemopump has been shown to be an effective left ventricular assist device. It is capable of supporting the circulation in patients with profound left ventricular dysfunction in the setting of cardiogenic shock. In experimental animals it seems possible that supporting the circulation immediately prior to reperfusion will produce a significant decrease in infarct size, which has important clinical ramifications, particularly in the setting of patients with large anterior myocardial infarction. The mechanism for this infarct salvage is unclear at the present time and requires further investigation, at a more basic level. The current tools available to the cardiologist include the intraaortic balloon pump and the cardiopulmonary support system (CPS), (PCs, BARD, Inc.). The Hemopump is available in Europe, but not in the United States at the present time. Clearly, the CPS system is the most powerful of the devices available, producing up to 61/m of flow. Unfortunately, there are a number of drawbacks with the CPS system, including its need for an oxygenator, which limits its useful period of support to approximately 8 hours. Additionally, support with the PCS system may be associated with adverse physiological events. The intraaortic balloon pump requires synchronization with the cardiac cycle, and hence, is not suitable for patients with significant tachyarrhythmias. Patients with overt cardiac arrest, similarly, cannot be supported with the intraaortic balloon pump. Nonetheless, the balloon pump has been associated with improved infarct salvage in an experimental animal model. On the other hand, the Hemopump, in its first version, required a surgical incision and placement of a graft onto the femoral artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Emergency use of cardiopulmonary bypass

Emergency cardiopulmonary support has been used in the United States since 1986. Physicians at participating centers for the National Registry of Elective Supported Angioplasty have contributed data on emergent cardiopulmonary support from their institutions. Results were analyzed to assess the benefits of cardiopulmonary support in patients with hemodynamic collapse. Patients with either cardiac arrest or hemodynamic collapse with cardiogenic shock unresponsive to pressor agents were placed emergently on cardiopulmonary support. Subsequent treatment comprised either angioplasty or surgical revascularization. Patients placed on cardiopulmonary support in < 20 minutes experienced a 41% survival rate across the entire registry of the participating centers of the National Cardiopulmonary Bypass Registry. Two centers with considerable experience demonstrated a 69% survival rate. Patients treated with emergency cardiopulmonary support because of hemodynamic collapse showed improved survival over any other hemodynamic support system. Results have improved for survival with increased operator experience, particularly in the early application group.

Regional flow adjusted hemoperfusion during coronary angioplasty: circulatory support/myocardial protection

Routine percutaneous transluminal coronary angioplasty catheters are adequate and demonstrate high success rates in balloon angioplasty with stable patients. Active hemoperfusion seems to offer an advantage in patients with hemodynamic instability. Active hemoperfusion provides myocardial protection during coronary interventions and can be applied in conjunction with routine angioplasty equipment. When compared with other devices demonstrating clinical utility in a supported angioplasty setting, this flow adjustable active antegrade hemoperfusion pump appears reliable, simple to use, cost-effective, and requires much less instrumentation than the more bulky CPS systems.

Clinical use of the Hemopump cardiac assist system for circulatory support

We have used the Hemopump in 15 patients in whom weaning from cardiopulmonary bypass was unsuccessful. The median time for the patients having the device on was 1.6 days postoperatively. They spent an average of 6 days in the intensive care unit and had a total hospital stay of about 17 days. Nine of 15 patients (60%) survived and were able to leave the hospital. There were some reversible decreases in kidney function in all patients, but none of them needed hemodialysis. Coronary artery bypass grafting supported by the Hemopump instead of cardiopulmonary bypass and with the use of a short-acting beta-blocker, esmolol, was carried out successfully in 12 patients. In this method the blood is oxygenated by the patient's lungs and the heart is perfused with its own warm blood. The Hemopump supports the circulation and if the patient needs circulatory support after the operation, a left ventricular assist device is already in place. There were no device-related complications apart from two initial cable fractures. The Hemopump fits well in the intensive care unit environment; it is silent, and the management of the console is easily learned. The Hemopump has shown to be an effective and safe tool for unloading the left ventricle while maintaining multiorgan perfusion. There are several potential applications for surgeons and cardiologists.

New technologies in the treatment of severe cardiac failure: the Texas Heart Institute experience

Various mechanical alternatives for the treatment of severe cardiac failure are currently in clinical use, and new mechanical devices are under preclinical and clinical investigation in laboratories around the world. These devices include the intraaortic balloon pump, left heart bypass pumps, left ventricular assist devices, and total artificial hearts. I describe briefly the devices and their applications with which my colleagues and I at the Texas Heart Institute have had experience.

Left ventricular assist without thoracotomy: clinical experience with the Dennis method

A method to provide left ventricular circulatory assistance without thoracotomy was developed and implemented in 2 patients. The left atrium is cannulated from the neck by passing a catheter across the interatrial septum (Dennis technique) using fluoroscopic and echocardiographic imaging. To facilitate ambulation, the arterial catheter is connected to the right axillary artery. Left atrial to axillary arterial flow is produced by a centrifugal pump. Two patients were perfused at 2.7 to 3.5 L/min for 5 and 6.5 days. One patient had successful coronary angioplasty during perfusion and remains alive 1 year later. The other patient died of sepsis and anuria that preceded implementation of circulatory assistance. The Dennis method of continuous left ventricular circulatory assistance avoids thoracotomy, requires a minimal operation, is portable and inexpensive, uses widely available equipment, and is particularly suitable for patients in cardiogenic shock after acute myocardial infarction. The method is safe and cost-effective, and merits wider application in selected patients.

Transvalvular left ventricular assistance in cardiogenic shock secondary to acute myocardial infarction. Evidence for recovery from near fatal myocardial stunning

OBJECTIVES

The purpose of this study was to test the hypothesis that transvalvular left ventricular assistance would support the circulation in patients with cardiogenic shock secondary to acute myocardial infarction and allow recovery of function in patients with a reversibly damaged (stunned) left ventricle.

BACKGROUND

Cardiogenic shock occurs in 7.5% of patients presenting with acute myocardial infarction, resulting in survival of only 20%. Despite the use of aggressive interventional therapy in patients with shock secondary to anterior myocardial infarction, survival remains as low as 33%.

METHODS

We studied 11 patients with acute myocardial infarction and cardiogenic shock, as defined by a cardiac index < 2 liters/min per m2, pulmonary capillary wedge pressure > 18 mm Hg and systolic blood pressure < 90 mm Hg during positive inotropic therapy. Patients were 57 +/- 13 years old (mean +/- SD) and had a mean left ventricular ejection fraction of 25 +/- 11%, mean arterial pressure of 69 +/- 13 mm Hg and mean cardiac index of 1.6 +/- 0.4 liters/min per m2 on admission to the study.

RESULTS

During the 1st 24 h of left ventricular assistance, pulmonary capillary wedge pressure decreased from 26 +/- 4 to 16 +/- 4 mm Hg (p = 0.01), cardiac index increased from 1.6 +/- 0.4 to 2.4 +/- 0.4 liters/min per m2, and the dopamine hydrochloride dose decreased from 51 +/- 92 to 18 +/- 12 micrograms/kg body weight per min. In survivors, cardiac index improved to 3.2 +/- 0.5 liters/min per m2 (p = 0.01), and left ventricular ejection fraction improved to 34 +/- 5% (p < 0.05). The overall survival in the study group was 4 (36%) of 11 patients (95% confidence interval [CI] 8% to 65%), and 4 (66%) of 6 patients (95% CI 29% to 100%) with a Q wave anterior myocardial infarction survived.

CONCLUSIONS

Transvalvular left ventricular support during cardiogenic shock complicating acute myocardial infarction is feasible and results in significant hemodynamic and functional improvement.

Mechanical left ventricular unloading during high risk coronary angioplasty: first use of a new percutaneous transvalvular left ventricular assist device

A new catheter mounted, transvalvular left ventricular assist device has been designed for percutaneous transfemoral access. The device, the Hemopump [14 French (Fr.) outer diameter], is based on a mixed flow rotary pump and is capable of flow rates of 1.5-2.2 l/min. The pump is inserted using a specialized 16 Fr. femoral introducer sheath. The first application of the percutaneous Hemopump in man was performed in two patients with hemodynamic compromise during high risk coronary angioplasty. In these patients, Hemopump support resulted in hemodynamic stabilization (increase in aortic pressure from 60/42 to 87/61 and from 80/60 to 100/70 mm Hg, respectively) and marked left ventricular unloading (decrease in pulmonary capillary wedge pressure from 25 to 10 and from 14 to 10 mm Hg) during balloon inflation. In both patients, percutaneous transluminal coronary angioplasty (PTCA) could be accomplished successfully. Using the system for periods of about 2 hr in each patient, we observed no vascular, hemorrhagic, or embolic complications. In both patients, only a minor increase in both plasma free hemoglobin and lactate dehydrogenase levels was noted. Our preliminary experiences suggest that the percutaneous Hemopump is safe and effective and may be a powerful alternative to other devices used for supported angioplasty.

Development of the Baylor/NASA axial flow ventricular assist device: in vitro performance and systematic hemolysis test results

Our newly developed axial flow pump consists of a flow tube, an internal rotating impeller, and a fixed flow stator (we call the stator) behind the impeller. This pump produces a flow of 3 to 8 L/min against 50 to 150 mm Hg pressure difference, respectively, in the range of 10,000 to 16,000 rpm. An axial flow pump that will be used as a ventricular assist device (VAD) has to have low hemolytic and good antithrombogenic characteristics. This paper will show how to decrease the hemolytic properties of this axial flow pump systematically using a test matrix. The test variables evaluated were impeller blade tip geometry, impeller flow tube clearance (radial clearance), impeller stator clearance (axial clearance), impeller blade number, stator blade number, and impeller length. All in vitro hemolysis tests were performed at 5.0 L/min against 100 mm Hg pressure difference using a total of 83 bags of fresh bovine blood. The results were as follows: the impeller blade tip geometry did not significantly effect hemolysis, a 0.005-inch and a 0.009-inch radial clearance were significantly (p < 0.01 or 0.001) less hemolytic than the other clearances, a 0.075-inch axial clearance was significantly (p < 0.05) more hemolytic than the other clearances, two- and six-bladed impellers were significantly (p < 0.01 and 0.02, respectively) less hemolytic than a four-bladed impeller, a five-bladed stator was significantly (p < 0.05 or 0.01) less hemolytic than the other stators, and the impeller length did not make a significant difference. Currently, the best index of hemolysis is 0.031 +/- 0.018 g/100 L, and using parameters from these results, implantable devices are being fabricated.

Pharmacologic and mechanical methods of discontinuing extracorporeal circulation in patients with heart failure

Separation from EC requires simultaneous optimal manipulation of heart rate and rhythm, loading conditions, afterload, and contractility. Patients with preexisting ventricular dysfunction will have alterations in beta-adrenergic receptors and responsiveness to catecholamines, but patients with previously normal ventricular function can also develop ventricular dysfunction. Catecholamines, by stimulating beta-adrenergic receptors, decrease systolic function to allow separation from EC. The phosphodiesterase inhibitors provide both inotropic support and vasodilation, to improve both systolic and diastolic function. When administered in combination, catecholamines and cyclic-AMP-specific phosphodiesterase inhibitors can have additive effects to restore beta 1-adrenergic responsiveness. Combination therapy provides an important support during biventricular dysfunction and facilitates separation from EC. Finally, mechanical support provides a therapeutic option when pharmacologic therapy is ineffective.